1. Field of Use
The present invention relates to the dental procedure of apicoectomy.
2. Description of the Related Art
An apicoectomy is a procedure used in dentistry in which the apex of a tooth is exposed surgically, the apex resected, and the area curretted. The procedure has been used for decades, perhaps even centuries, to provide relief from dental disease. A diseased tooth irritates the bone surrounding its root, causing pain and damage to the bone. An apicoectomy promotes healing of the bone and provides relief from pain by removal of the diseased apex of the tooth, which is typically the foremost cause of irritation.
Traditionally, the location of the apex has been determined in a variety of ways, none of which have proved to be very exact. In fact, the inexactitude of this determination is the primary factor in limiting the use of the procedure to cases where other treatments have not been successful. In the past, the operation has involved a high degree of risk of permanent nerve damage. The mandibular nerve is very close to the apices of the teeth in the mandible. To reach the diseased apex, a dentist must drill through the mandible. Typically, he makes an incision in the gum, reflects the tissue to expose the jaw bone and drills exploratory holes in the bone until he finds the apex of the tooth. Pieces of bone are then removed until the diseased area is found and entirely exposed. The more exact the initial approximation of the location of the apex, the less risk there is of drilling into the mandibular nerve and causing paresthesia. For years, dentists have sought a means of reducing the guesswork involved in determining the location of the apex.
One procedure which was developed is described in U.S. Pat. No. 1,417,237 to Evans. A probe is entered through the root canal of a diseased tooth to the point of emergence just beyond the root apex. The depth of the probe is measured by an external guide, so that a drill, directed by the guide from the exterior of the jaw, may be caused to penetrate the bone at right angles to the probe at the point where the latter has located the root apex.
An alternative method was later developed in which the physical guide structure of the Evans device was eliminated. U.S. Pat. No. 3,772,791 to Malmin discloses a system to measure the depth of the root canal by insertion of a probe into the root canal of the tooth. A measurement sleeve is secured to the probe and marked with indications of length so that the depth of the probe may be accurately determined by x-ray.
The Evans and Malmin patents both disclose instruments having probes which are inserted into the root canal of a tooth. The Evans device has an inflexible probe which is useful only in cases in which the diseased tooth has a straight, clear root canal. Any curvature of the root canal would prevent proper insertion of the probe. Therefore, in many such cases, the instrument would be useless. The Malmin device may successfully determine the length of even a curved root canal in preparation for root treatment, but it provides no guide for locating the apex of a tooth for surgical procedures. Neither device may be used on a tooth having a calcified root canal or on a tooth which has been previously treated and the root canal filled. In these circumstances, the root canal is blocked or filled so as to prevent the insertion of a probe.
Moreover, the risk of inexactitude still exists with the Malmin and Evans techniques. Both devices determine the depth of the root canal but neither provides an exact indication of where the dentist should drill to find the apex. The Evans device provides an external drill guide, but the guide is only accurate on a tooth having a straight root canal, and is useless if the root canal is calcified or previously treated. The Malmin device allows an x-ray to show the location of the apex, but provides no guide for drilling nor any means of measuring the position of the apex other than by its depth. The device is suitable for determining the length of the root canal prior to treatment, but is not suitable for surgical procedures.
The present invention eliminates the need for a straight, clear root canal by locating the apex of the tooth with an external guide and measuring device. Because of the two-dimensional freedom of the guide, the location of the apex is determined to a greater certainty than is possible simply by determining its depth. The procedure described below, made possible by the present invention, permits the dentist to locate the exact apex of a tooth without removing any bone, and consequently, without a high degree of risk of nerve damage. The procedure is also applicable to filled or calcified teeth because it is not necessary to insert a probe into the root canal of a diseased tooth.